As described in patent application WO2005061311A1, for example, a car chassis made by joining a plurality of extruded element comprises a plurality of linear bars, which have a constant section, are made by extrusion, and are joined to one another by welding at structural nodes defined by junction bodies provided with pockets for accommodating the head of the linear bars.
Some linear bars may not be monolithic but must imperatively be composite (i.e. made of several parts) and removable (i.e. the parts are connectable and disconnectable from one another) to allow some particularly large parts of the car (typically, but not only, the thermal engine and the gearbox) to be assembled and disassembled. A composite bar is made by joining several extruded elements which are butt jointed to one another. Currently, the butt jointing of the two extruded elements includes using junction bodies which rest on the two extruded elements and are fixed (typically by means of screws) to both extruded elements; several junction bodies with flat cross section or junction bodies with a with an either “L”-shaped or “U”-shaped cross section are required to confer an adequate stiffness to the butt joint. However, using the junction bodies implies both an increase of the overall weight of the chassis (the weight of the junction bodies is “wasted” because the only function of the junction bodies is to make some parts removable) and an increase of dimensions (the junction bodies locally increase the size of the linear bar).
DE3811427A1 and EP0631924A1 describe a composite bar for the chassis of a vehicle which consists of two extruded elements which are butt jointed together at a junction area. Each extruded element has a trapezoidal cross section having a major base, a minor base parallel and opposite to the major base and two side walls; furthermore, one end of an extruded element arranged in the junction area has no major base. In the composite bar described in DE3811427A1 and EP0631924A1, the end of an extruded element has a deformation so that the cross section of the end of the extruded element may be axially inserted without interference into one end of the other extruded element. However, the need to locally deform the end of an extruded elements implies a further mechanical machining which complicates the machining of the extruded elements and may locally reduce the mechanical strength at the deformation itself.